The present invention relates generally to therapeutic heat packs. More specifically, the present invention relates to a therapeutic heat pack utilizing a water absorbent filler containing polyacrylamide.
Application of hot and cold compresses to a patient is a standard medical practice for reducing inflammation and pain. Further, hot and cold compresses are often used for increasing blood flow to various parts of the anatomy. Cold compresses are generally recommended for the first 24 to 48 hours after an injury, such as a sprain, to reduce swelling and retard inflammation. Thereafter, heat is recommended due to its desirable therapeutic effects. Specifically, heat produces the following therapeutic effects: 1) it increases the extensibility of the collagen tissue; 2) it decreases joint stiffness; 3) it produces pain relief; 4) it relieves muscle spasms; 5) it assists in resolution of inflammatory infiltrates, edema, and exudates; 6) it increases blood flow; and 7) more recently, it has been used as part of cancer therapy. See Lehmann, Therapeutic Heat and Cold, pp. 404 (3rd edition, 1987).
Preferably, moist heat is recommended due to its proven ability to increase blood flow--hyperemia. Moreover, moist heat is recommended for the reduction of pain and inflammation of arthritis and bursitis, rheumatic conditions, headaches, and many common ailments, such as sore muscles, cramps, back and neck pain.
For almost one hundred years, hot water bottles have been used effectively in home health care. However, they do not provide the additional benefits of moist heat. Further, because of their design, hot water bottles are not suitable for limbs.
Moist heat packs that have been in general use by medical professionals for over thirty-five years are filled with a bentonite clay in a canvas fabric. For example, U.S. Pat. No. 2,710,008 to Jensen illustrates such a moist heat pack filled with bentonite clay. When the moist heat pack is immersed in water, the bentonite filler readily absorbs a large volume of water. Over the years, these bentonite-type moist packs have been the primary device used for moist heat therapy.
However, bentonite-type moist packs possess a number of limitations. For instance, bentonite clay packs are substantially rigid when hydrated and do not readily conform to areas of a patient's anatomy. When fully hydrated, the bentonite clay has a consistency similar to toothpaste. Since the bentonite is neither soft nor supple, it is not comfortable when applied to the body. As described in the '008 patent, hydrated bentonite has a stiff paste-like consistency, rendering the moist pack substantially rigid.
Further, bentonite-type heat packs lack a substantially high heat retention. Bentonite clay when hydrated consists of about eighty percent water. While it expands to fourteen times its dry bulk, retaining an amount of water equal to four times its dry weight, it only retains heat for 25 to 30 minutes.
Bentonite clay presents another major problem in that once it is hydrated it needs to be maintained in a hydrated state, i.e. immersed in water. After hydration, the bentonite permeates the fabric covering. If allowed to dry out, it causes the fabric to be brittle and easy to rupture. The bentonite forms into a rock-hard brick, which can require several days of immersion in water for re-hydration. While this limitation does not present a serious problem in a professional setting, since moist packs are generally stored in water baths at a constant temperature of about 165.degree. F., this does present a serious problem for occasional use at home. The limitation, in effect, makes these packs unsuitable for home use, due to the trouble in maintaining them in a hydrated state.
Bentonite clay is also subject to fungus growth requiring a fungicide in the manufacturing process. Likewise, it is subject to acquiring a bad odor, thus necessitating frequent maintenance with disinfectants and deodorizers.